In work vehicles such as backhoe loaders, power is transmitted from an engine to a differential through a transmission, and is further transmitted from axles to wheels through final reducers. Further, brake devices are mounted between the differential and the final reducers in order to brake rotation of the axles.
Brake devices of this type are disposed inside an axle housing and a gear housing, and employ a wet multi-plate hydraulic braking type. Specifically, the housing accommodates brake units, each of which is formed by a plurality of brake disc plates and a piston to be actuated by means of hydraulic pressure. Further, the piston is actuated by means of brake hydraulic pressure to be supplied thereto from the outside, and the plural brake disc plates are pressed to each other. Accordingly, a rotary member such as an axle is configured to be braked.
Some of such brake devices are provided with a slack adjuster mechanism in order to prevent the stroke of the piston from being changed from its initial state even when the brake disc plates are abraded.
For example, in a device described in Japan Laid-open Patent Application Publication No. JP-A-2001-193773, an adjustment screw making contact with a piston is provided while being operable from the outside of a cylinder. A return position of the piston is adjusted by the adjustment screw. The aforementioned slack adjuster mechanism described in the above mentioned publication is of a mechanical type including the adjustment screw. However, a mechanism has been also provided that is configured to execute automatic adjustment by means of hydraulic pressure.